The present invention relates to a method of and apparatus for mounting an electronic part to a substrate conductor, in particular, to a method and apparatus for mounting an electronic part to a substrate which enables inspection of the bonding junction (made by flip-chip bonding) between the electronic part and the substrate conductor.
Conventionally, as a high-density mounting method of a semiconductor chip to a substrate conductor, a flip-chip bonding system has been utilized. Such a flip-chip bonding system works by forming a bump (either a soldered bump or metal bump) on an electrode of a semiconductor chip or an electrode of a substrate conductor, and joining the electrode of the semiconductor chip to the countered electrode of the substrate conductor via the bump, with the electrode of the semiconductor chip facing down.
Since in the flip-chip bonding system the electrode can be taken out from an arbitrary position of the surface of the chip, the connection with the substrate conductor by the shortest distance is possible. In addition, the size of the chip does not increase even if the number of electrodes increases, and super-thin mounting can be performed.
A soldering reflow method, an anisotropic conductive resin connecting method, a thermocompression bonding method, an ultrasonic wave, and the like, can be used to join the semiconductor chip or the bump provided on the electrode of the substrate conductor to the mated electrode in the flip-chip bonding method.
According to the ultrasonic wave and thermocompression bonding method mentioned above, and as shown in the conventional apparatus of FIG. 12, in a mounting apparatus 10 of a semiconductor chip 3 as an electronic part comprising an ultrasonic vibration generating device 8, a horn 7, a collet tool 6, a substrate conductor heating unit 4 and a control unit 9, and executes the ultrasonic wave and thermocompression bonding connection utilizing the flip-chip bonding system. In this bonding process, a substrate conductor 1 is heated by the substrate conductor heating unit 4, and an ultrasonic vibration is applied to the collet tool 6 on the side of the semiconductor chip 3 by the piezoelectric element 8 or the like via the horn 7, so that bumps 5 formed on the semiconductor chip 3 diffusively join to electrodes 2 of the substrate conductor 1.
In comparison with other methods, this ultrasonic wave and thermocompression bonding method has advantages such that a joint material is not required, the connection can be made in a short time, and the bonding can be performed at a comparatively low temperature.
However, when using the above-mentioned conventional ultrasonic wave and thermocompression bonding connection methods utilizing the flip-chip bonding system, propagation of an ultrasonic vibration is unstable, causing a danger of formation of defective connections. Such problems may be also caused by slippage between a rear surface (upper surface in the drawing) of the semiconductor chip 3 and the collet tool 6, diffusion of a vibration from the horn 7, and deterioration of the piezoelectric element 8 due to aging, when using the conventional apparatus shown in FIG. 12.
In addition, in the flip-chip bonding system described above, since the joined portion is hidden from view by the semiconductor chip 3, the joined portion cannot be visually inspected after the connection is made. Therefore, the occurrence of the defective joints can become a particularly serious problem.
The present invention has been devised to avoid such problems mentioned above, and its object is to provide a mounting method and a mounting apparatus for mounting an electronic part to a substrate conductor by means of the ultrasonic wave and thermocompression bonding connecting method utilizing the that flip-chip bonding system, while also being able to inspect the state of the formed joint, as was previously impossible with the conventional methods.
In order to achieve the above object, the present invention provides a first embodiment of a mounting apparatus of an electronic part utilizing ultrasonic wave and thermocompression bonding to form a flip-chip bonding system consisting of an ultrasonic vibration generating device, a horn attached to the ultrasonic vibration generating device, a collet tool for holding an electronic part attached to the horn, a control unit connected to the ultrasonic vibration generating device, a substrate conductor heating unit connected to the control unit, and a height measuring device, wherein the height measuring device for monitoring the height of the electronic part with respect to a substrate conductor is connected with the control unit.
In a second embodiment, a mounting method of an electronic part according to to the first embodiment is provided which includes lowering the electronic part having an electrode with respect to a substrate conductor having an electrode, applying a predetermined weight upon the electronic part when one or more bumps, which are provided on an electrode of the electronic part or an electrode of the substrate conductor, come into contact with a countered mating electrode, to compress the bumps and cause a first stage bump sinking amount, and then applying a predetermined weight and an ultrasonic vibration simultaneously on said electronic part for a predetermined time, to further compress the bumps, causing a second stage bump sinking amount, to form a connection between the electrode of the electronic part and the electrode of the substrate conductor.
The amount of compression of the bumps (bump sinking amount) due to application of the predetermined weight and an ultrasonic vibration for a predetermined time is monitored by a height measuring device, and the connection formed by ultrasonic wave and thermocompression bonding utilizing a flip-chip bonding system is judged defective or non-defective by making a judgment as to whether or not the bump sinking amount at the time of applying the ultrasonic vibration falls within a desired range.
In a third embodiment, a mounting method of an electronic part according to the second embodiment is provided, wherein the first stage bump sinking amount and second stage bump sinking amount are individually monitored by the height measuring device, and the connection formed by the ultrasonic wave and thermocompression bonding utilizing the flip-chip bonding system is judged defective or non-defective by making a judgment as to whether or not the respective stage bump sinking amounts fall within respective desired ranges.
In a fourth embodiment of the present invention, a mounting device of an electronic part having a bump for forming an ultrasonic wave and thermocompression bonding connection utilizing a flip-chip bonding system is provided consisting of an ultrasonic vibration generating device, a horn connected to the ultrasonic vibration generating device, a collet tool in connection with the horn, a control unit, and a substrate conductor heating unit in connection with the control unit, wherein a vibration measuring device for monitoring a vibrating state of the electronic part or the bump is connected with the control unit.
In a fifth embodiment of the present invention, a mounting method of an electronic part according to the fourth embodiment above, utilizing ultrasonic wave and thermocompression bonding methods in a flip-chip bonding system is provided for mounting the electronic part to a substrate conductor, wherein a vibrating state of the electronic part at the time of mounting is measured and compared with a reference waveform, a judgment made as to whether or not an ultrasonic vibration is applied normally and, using this information, the connection judged defective or non-defective.
In a sixth embodiment of the present invention, a mounting apparatus of an electronic part for forming an ultrasonic wave and thermocompression bonding connection utilizing a flip-chip bonding system is provided which consists of an ultrasonic vibration generating device, a horn connected to the ultrasonic vibration generating device, a collet tool attached to the horn, a control unit, and a substrate conductor heating unit connected with the control unit, wherein a measuring device for monitoring a voltage, an electric current, or both, to be applied to the ultrasonic vibration generating device, is connected with the control unit.
In a seventh and final embodiment of the present invention, a mounting method of an electronic part according to the sixth embodiment above, for forming an ultrasonic wave and thermocompression bonding connection utilizing a flip-chip bonding system, is provided, wherein a joint is inspected and judged defective or non-defective by applying and measuring a voltage and an electric current to an ultrasonic vibration generating device, and comparing the voltage and electric current, respectively, with reference waveforms to determine whether the voltage and electric current are applied normally in the mounting apparatus of an electronic part.
Specifically, while the defective or non-defective joint is compared with a reference, the mounting is performed by using means for monitoring a change (sinking amount) in the height of the bump present on the electronic part (ususally a semiconductor chip) at the time of the mounting, as described in the first, second and third embodiments described above, means for monitoring the vibrational state of the electronic part or bump at the time of the mounting, i.e., the amplitude, vibrating speed, vibrating velocity or the like as described in the fourth and fifth embodiment described above, and means for monitoring the voltage and electric current to be applied to the ultrasonic vibration generating device by utilizing a piezoelectric element as described in the sixth and seventh embodiment described above.